The present invention relates to magnetic hard disk drives and more particularly to vibration and power consumption. minimization in disk drive array systems.
Disk drives, also called disk files, are information storage devices that use a rotatable rigid disk with concentric data tracks containing the information, a head or transducer for reading and/or writing data onto the various tracks, and an actuator connected to a carrier for the head for moving the head to the desired track and maintaining it over the track centerline during read and write operations. The most common form of actuator is a rotary voice coil motor (VCM) actuator that moves the head carrier in a nonlinear, generally arcuate path across the disk. There are typically a number of disks mounted on a hub that is rotated by a disk drive motor, also called a spindle motor, and a number of head carriers connected to the actuator for accessing the surfaces of the disks. A housing supports the drive motor and head actuator and surrounds the heads and disks to provide a substantially sealed environment. In conventional magnetic recording disk drives, the head carrier is an air-bearing slider that has an air-bearing surface (ABS) designed to enable the slider to xe2x80x9cflyxe2x80x9d or ride on a bearing of air above the disk surface when the disk is rotating at its operating speed. The slider is maintained next to the disk surface by a biasing force from a suspension that connects the slider to the actuator. The suspension is attached to a rigid arm connected to the actuator.
Contact start/stop (CSS) disk drives operate with the slider in contact with the disk surface during start and stop operations when there is insufficient disk rotational speed to maintain the air bearing. To minimize the effect of xe2x80x9cstictionxe2x80x9d, i.e. the static friction and adhesion forces between the very smooth disk surface and the slider, CSS disk drives often use a dedicated xe2x80x9clanding zonexe2x80x9d where the slider is parked when the drive is not operating. The landing zone is typically a specially textured non-data region of the disk. In contrast to CSS disk drives, xe2x80x9cload/unloadxe2x80x9d disk drives address the stiction problem by mechanically unloading the slider from the disk when the power is turned off, and then loading the slider back onto the disk when the disk has reached a speed sufficient to generate the air bearing. The loading/unloading is typically done by means of a ramp that contacts the suspension when the actuator is moved away from the data region of the disk. The slider is thus parked off the disk surface with the suspension supported in a recess of the ramp. Load/unload disk drives are more commonly used in a laptop and notebook computers because the parking of the slider on the ramp away from the disk surface also provides some resistance to external shocks caused by moving or dropping the computer.
To improve the performance of disk drives, particularly the rate at which the recorded data can be accessed, it is desirable to rotate the disks at high RPM. In addition, it is desirable to place the data tracks as close together as possible to maximize the data storage capacity. However, when conventional disk drives, such as commercially available 3.5 inch and 2.5 inch form factor drives, are rotated at high RPM they consume excessive power and generate excessive heat in the disk drive housing. In addition, high speed disk rotation causes airflow-induced disk xe2x80x9cflutterxe2x80x9d and vibration of the suspension and/or arm, which makes it difficult for the read/write head to locate the proper data track. This is referred to as track misregistration (TMR).
While individual disk drives are typically used in personal computers, disk drive array systems are used with mainframe computers because mainframe computers require a very large amount of disk storage capacity. Disk drive array systems are typically 200 or more individual disk drives connected and housed together to provide a large storage capacity. Since there are so many disk drives operating at once in a confined housing space, vibration, power consumption, and heat dissipation becomes even more of a concern.
The use of a hermetically sealed disk drive housing containing a gas other than air, such as helium, to reduce the effect of heat generation within the housing has been proposed, as described in U.S. Pat. No. 4,367,503 and Japanese published patent application JP8077527A. IBM Technical Disclosure Bulletin, Vol. 23, No.9 (February 1981), pp. 4310-4311, describes a removable disk pack mounted on a drive apparatus that uses reduced air pressure around the rotating disks to reduce the effects of heat generation and air turbulence. Japanese published patent application JP7021752A describes a test apparatus that uses a vacuum pump to remove air from within the test chamber for the purpose of testing the head carrier-disk interface. Japanese published patent application JP10222960A describes an optical CD-ROM drive with a vacuum pump for removing air to decrease air resistance and eliminate dust particles.
A need therefore exists for providing a disk drive array system where the disk drives within can operate at high disk RPM without consuming excessive power and without generating disk flutter or vibration of the suspension arm.
A principle objective of the present invention is to provide a disk drive array system wherein the disk drives consumes less power and causes less vibration when run in high RPM.
In view of the forgoing objectives, an embodiment of the present invention provides a disk drive array system that utilizes a vacuum pump to reduce the internal pressure of the disk drives during operation. The vacuum pump is control by a pump controller that receives a pressure indicating signal from a pressure sensor. The pump controller maintains the disk drive internal pressure to a predefined reduced pressure, 0.5-0.6 atm for example. Because of this reduced internal pressure, disk drives with an ABS designed to operate at such reduced pressures have to be used.
In another embodiment of the present invention, helium is circulated in the disk drives in a disk drive array system. Helium provides the same benefits of reducing vibrations and power consumption, but also the added benefit of better thermal conductivity compared to air and thus has better cooling.
A third embodiment of the present invention involves the use of a vacuum pump to achieve a reduced internal pressure and also a helium circulator to circulate helium in the disk drives in a disk drive array system. This embodiment combines the benefits of the reduced internal pressure environment as well as the better thermal conductivity of a helium environment.
In all the embodiments, the disk drive array system must be configured such that removing an individual disk drive will not affect the internal pressures of the remaining disk drives.